Means for reproducing sound



ul 12 1927. I J y H. J. ROUND MEANS FOR REPRODUCING SOUND Filed Feb. 2, 1924 mu-FEEnzcmh uzcxnudh 0E m uozorrcjancz mom Pam .50

25E ozGaQEE E9; :mSQ EH55 mu M4025 m. M M 3 Mn W m w. h AYB thisart and need not Patented July 12, 1927.

UNITED STATES.

PATENT OFFICE. r

COBPORA'I'IOII OI AMERICA, A CORPORATION OF DELAWARE.

mums FOB nnrnono'cmo SOUND.

Application filed February 2,

The object of this invention is to provide sound reproducing means in which the distorting effects due to the natural tone of a diaphragm may be substantially eliminated.

According to this invention I employ a plurality of diaphragms of different pitches, each with its own electromagnetand the input coils of the magnets being connected together preferably in series, and I preferably arrange a shunt across one or more of the magnets.

In the drawings Fig. 1 is a diagrammatic representation of an arrangement in accordance with the invention;

Fig. 2 is an illustration of of magnetophone;

Fig. 3 shows an arrangement in which a combination of resistance, inductance and capacity is used for damping and Figs. 4 and 5 are diagrammatic represcntations of an arrangement in which tuned a suitable form circuits are utilized for controlling the.

damping of different audible frequencies.

Referring to the arrangement shown in Fig. 1, A B C are three magnetophones with their input coils connected in series and with adjustable resistances a b 0 arranged across the coils.

, The term input coil is used hereto distinguish the coil G shown in Fig. 2 from the coil H. The coil H is a polarizing coil which may be energized from an independent source in a manner which is well-known in be described further here.

When sound waves fall upon the three diaphragms the amplitude of the currents due to the -In0venients of the various diaphragms can be adjusted by adjusting the resistances, so that a larger or smaller current can be produced by any particular diaphragm of the combination as is found desirable. The shunts have the double effect of giving the correct strength and also of dan'ipingthe combined mechanical and electrical circuit. I

Similarly, when currents due to sound are led through the coils of the magnets, the amplitude of the vibrations of any particular diaphragm can be adjusted at will by adjusting the shunts.

The diaphragms of difierent pitches may be constructed of 1I0I1 of difierent thickness invention.

1924, Serial No. 690,221, and in Great Britain February 5, 1923.

and diameters. The diaphragms should be well damped by means of washers of india rubber or the like and should, be mounted in heavy rigid cases.

Figure 2Ishows a form of magnetophone specially suitable for use in carrying out my Dis a heavy rigid case in the front of which is mounted a diaphragm E behind which is a pole piece F surrounded by the active coil G and a polarizing coil H, the case acting as the return circuit. J are pads of rubber or other suitable material which can be pressed by means of screws K working in brackets L against the diaphragm to damp it.

1 i In cases where suificient dampmg cannot be obtained I can place in the'circuit capaclt resistance, inductance arrangements the diaphragms at their resonant points.

Figure 13 shows such an arrangement where M N are two rejector circuits containing resistance, capacity and inductance placed across a' combination of two magnetophones A B.

, for tie purpose of weakening the-eifect ot' 1 have found that a very good reproduction ofthe human voice can be obtained by employing two diaphragms one having a natural tone of about 6000 per second and the other a tone of about 600 per second, this latter being shunted since it is more sensitive than the former. For the reproduction of music in which bass is present a suitable combination consists of three diaphragms whose natural tones may be 200, 900. and

6000, while a still better combination consists of five, diaphragms whose tones are about 200, 500,900, 2,000 and 8,000.

According to a modification of my invention I connect or couple to the electromagnet of a diaphragm having a moderately high pitch, say, 2000, a pluralit 1n parallel, each circuit select a different range of frequencies, and I then amplify one or more of these-ranges as desired and then resynthesize the results. Such an arrangement is shown in Fig. 4. In series with the coil of the magnetophone A are arranged three coils P, P and P of filter circuits eing adapted to which are .coupled to three circuits Q Q Q, tuned to different ire uencies and connected to the rids and aments of three valves R R 8 by which the oscillations combination of a plurality of diaphragms,

in these circuits Q Q Q3 as desired and conveyed to the line through other amplifying valves 8, S and S It is obvious that in any of these arrangements instead of using a magnetophone I may use any other proportional device such as an electrostatic telephone or the piezo electric effect.

In a loud speaking telephoneI employ a single horn of great effective length so that it is practically equally resonant to all periods above, say, 100 per second, and I arrange on the base of this a plurality of diaphragms with shunted magnets as above described or a single diaphragm to which is applied a current distorted by parallel filter circuits as above described.

Having described my invention what I claim is p 1. In means for reproducing sound, a plurality of diaphragms of different pitches each having its own' electromagnet and the coils ofthe magnets being connected together and a shunt across one or more of the magnets.

2. In means for reproducing sound, the

can be amplified an electromagnet in proximity to each diaphragm, a plurality of circuits coupled to the circuits of the magnet and adapted to select diflerent ranges of frequencies and means for amplifying selectively one or more of these ranges of frequencies.

3. In a device for amplifying broad band high frequency oscillations, a plurality of oscillatory circuits tuned to independent frequencies, separate means associated with each of said oscillatory circuits to amplify the oscillations received thereby, each of said amplifying means being independently variable, and a separate acoustic device associated with each of said amplifying means.

4. In, means for reproducing sound a source of current of a plurality of audible frequencies, a plurality of acoustic means selectively responsive to different ranges of I frequencies .in. said source and means for corresponding to one or more controlling the response of one or more of said selective means to control the reproducent natural periods and said electromagnets being energized from the same source and a rejector circuit associated with each electromagnet for damping currents of a frequency of the natural periods.

7. Means for reproducing sound comprising the combination of a plurality of diaphragms and an electromagnet for each diaphragm, said diaphragms having difi'erent natural periods and the coils of said electromagnets being connected in series and a shunt across one or more of the coils.

' 8. The method of reproducing broad band oscillations which com rises impressing said oscillations upon a purality of magnetophones each of which is provided with an input coil and an associated diaphragm having a natural vibration frequency and controlling the output of each magneto-phone by varying the effective resistance of its associated input coil.

9. The method of amplifying broad band high frequency oscillations Which comprises the steps of separating the broad band into narrow band frequencies, amplifying the narrow bands, separately varying the egree of amplification of the separate narrow bands, and finally combinin the narrow bands in .a single instrumenta it HENRY-JOSEPH ROUND.

reproducing sound com- 

